If the "pilot shortage" really does happen the first people DAL, AAL, and UAL will hire will probably be pilots from the ULCCs and LCCs. After all, they're the biggest direct threat/competition.

Look at Piedmont and Frontier. Apparently Frontier loves some Piedmont pilots. If AAL was really desperate they could immediately start hiring pilots from Frontier.

The same thing with JetBlue and United. Etc. Etc.

Say what you will about them hiring military pilots. If a shortage really does happen, and it's as desperate as everyone says, poaching from other pilot groups will be the telling sign.

Until then, it'll be easier, but not easy. (just my opinion of course)